What's are these?

[William_H]

I plan on leaving well alone. I have plenty of charging with solar and a water cooled genny and the solar meter tells me the charge of each bank so the alternator charging is pretty much incidental. I just wanted to identify the components to understand what they were doing. Thanks.

I can appreciate your sentiment. However as said it would be well worth checking the voltage of the batteries when being charged by the engine alternator alone. You might have found you get by OK as is but the time might come when you need that engine alternator charging. (No sun, generator kaput). The main engine alternator will have a regulator which senses the charge voltage and controls it to about 14volts. (just like your car) Now many alternator regulators are mounted on the alternator and take the sensing of the output at the actual output (heavy) lead of the alternator. Now in a car or a one battery installation this is fine becausae this output wire goes straight to the battery pos terminal. (perhaps via switch)
Diodes are one way valves and if the alternator output goes through 2 diodes one for each battery (engine and domestic) then both batteries receive charge but due to one way nature of the didoes the 2 batteries are otherwise isolated. ie the engine battery can't feed you lights but your domestic battery can't feed the starter motor. This isolation is the desired outcome. We can flatten the domestic battery over night but engine start battery has not been discharged.
There aree some zero volt drop diode devices but generally most diodes are simple silicon diodes. These inevitably drop .7 volt and more with more current. Thsi means that the voltage as sensed by the alternator might be 14v but after going through the diodes both batteries will only be charged at 13.3 or less volts. At that voltage the batteries will only ever be half charged. (no good). One answer is to move the regulator voltage sensing wire from the output of the alternator to one of the batteries. So the regulator increases its output to allow for diode losses. Unfortunately because most alternators are made for cars getting access to this wire is not always easy. Smart charge regulators an external regulator can easily be set to battery sense but these usually require surgery to the alternator to disconnect the internal regulator.
The alternative as said is to fit a VSR.This is a voltage sensing relay. Here the alternator is connected to the engine battery and the domestic battery sytem is entirely separate. Except that when the engine alternator is charging a relay contact connects both batteries together. Being a metal contact there is no voltage drop. The relay measures the voltage of the engine battery and operates when the voltage rises to 13v. This is sometimes adjustable but is typical of the engine battery voltage after it has been charged for a few minutes. A relay could be operated by an oil pressure switch or even manualy by 1,2,both switch. The disadvatage of the switch is that you must remember to isolate the domestic battery after enginbe shut down.
So it would be good for you to just check and see what voltage the alternator is charging at. Around 13.75 to 14 would be good. If it goes to 15 or 16 you have a smart charge regulator and this should later drop to 13.75. If the best batteries rise to is 13volts then you should modify the system accordingly.
Yes youare right to sort out wiring. Sure as anything you will need to understand it all soon enough.
The "shunt' on the left is used to sense current flow. Samll amp meters have a shunt built into the meter case but for large currents hence large wires a remote shunt is more usefull. So the fat wires carry the actual current to be measured. The light wires attached to each end carry the small voltage developed across the shunt to the meter.
The shunt is just a piece of metal which has a finite and calibrated resistance so that typically 200 amps through the shubnt will drop 200millivolts. (100amps 100mv etc)
It is likely part of your BM-1 monitoring system where current is displayed as well as being sued to claculate total amp hours in and out. The tricky part witha shunt is to figure out which currents flow through it so are measured. They are often connected in the negative wire of a battery to measure total in and out. Yours being connected to the diodes means it is in positive line. Incidentally if it is in the positive line then those 2 wires are connected to a high current source. Such that any short to negative of either wire would result in very high current through the light wires. They would get red hot producing smoke and potentially a fire. For full protection they shou8ld have fuses in each wire appropriate to the current rating of the small wires. If theya re in negative line then usually less concern.
good luck olewill

 

[VicS]

I have a Victron Cyrix

Isn't that a "wimmins" complaint ...... or an excuse, " not tonight I have a victron cyrix."

 

[nigelmercier]

... VSR's are often recommended here for charge splitting, but IMO it could be worth thinking over if it is a good idea to bring the starter battery online when charging the house bank from shore power...

Definitely not a good idea. I've wired mine so it doesn't fire unless the ignition is on.

 

[john_morris_uk]

Until VSR's appeared, diodes were the best new thing!!!! But hey that's progress..

Using progress in this context implies that a VSR is 'better' than diode splitters. Whilst it certainly is better if the diodes are used ignorantly and incorrectly, moving to an automatic mechanic switch (Which us what a VSR is) is just another option and certainly not 'better' than a correctly wired split diode system. I pointed out the disadvantages of such a system, but I suspect that there's a lot of 'I did it this way, therefore my way is THE way in this discussion. (Like so many discussions on these forums...)

All IMHO of course...

 

[pvb]

Perhaps one factor worth taking into account is the failure method of diodes and VSRs.

Diodes usually fail open circuit. If the diode leg supplying the battery with the battery-sensing lead attached fails open circuit, the alternator voltage will soar and it will cook the other battery. In many cases, the first you'll know is the awful acrid smell of boiling acid. I've seen the results of this on a boat with an Adverc regulator sensing the domestic bank.

If a VSR fails, one battery just doesn't get charged - not the end of the world, and no other damage.

 

[sailinglegend420]

..Diodes usually fail open circuit. If the diode leg supplying the battery with the battery-sensing lead attached fails open circuit, the alternator voltage will soar and it will cook the other battery....

If a VSR fails, one battery just doesn't get charged - not the end of the world, and no other damage.

That's the best reason yet that I've heard for going VSRs. One of our split diodes went open circuit and the starter battery went flat. Luckily the voltage sense was on the alternator.

With split diodes the voltage sensing must never be on one of the batteries for another very good reason.

Consider a heavily depleted large service bank - and an almost full smaller starter battery. The voltage drop across the diode feeding the service bank increases with the current so may well reach 1.4 volts or more. If the alternator senses the voltage at the service bank it will raise the alternator output by 1.4 volts to say 15.8 volts to get 14.4v at the battery. The voltage drop across the diode feeding the starter bank is only 0.7 volts because the smaller service bank is taking a much much smaller current. So the starter battery is sitting at 15.1 volts for maybe several hours! This is almost an equalizing charge - so not very good for any sealed, Gel, and AGM batteries.

 

[halcyon]

Definitely not a good idea. I've wired mine so it doesn't fire unless the ignition is on.

What is your reasoning behind this statement ?

Brian

 

[sailorman]

Isn't that a "wimmins" complaint ...... or an excuse, " not tonight I have a victron cyrix."

No problem if your quick, it takes 10 minutes before it "kicks-in" so not an issue for me

 

[BabaYaga]

Consider a heavily depleted large service bank - and an almost full smaller starter battery. The voltage drop across the diode feeding the service bank increases with the current so may well reach 1.4 volts or more. If the alternator senses the voltage at the service bank it will raise the alternator output by 1.4 volts to say 15.8 volts to get 14.4v at the battery. The voltage drop across the diode feeding the starter bank is only 0.7 volts because the smaller service bank is taking a much much smaller current. So the starter battery is sitting at 15.1 volts for maybe several hours! This is almost an equalizing charge - so not very good for any sealed, Gel, and AGM batteries.

This reasoning assumes that the alternator is able to put out 14,4 V into a large, heavily depleted service bank. Is that realistic?
I think in most cases the voltage initially would be at 13,5 or lower and only reach 14,4 when the bank's SOC gets close to 75 - 80 percent.
At that point the current will be much lower and the voltage drop over the service bank diode will be more or less similar to that of the starter battery's.

 

[sailorman]

This reasoning assumes that the alternator is able to put out 14,4 V into a large, heavily depleted service bank. Is that realistic?
I think in most cases the voltage initially would be at 13,5 or lower and only reach 14,4 when the bank's SOC gets close to 75 - 80 percent.
At that point the current will be much lower and the voltage drop over the service bank diode will be more or less similar to that of the starter battery's.

The Victron Cyrix has a 2 fold delay built in, either when ? voltage is attained or 10 minutes

 

[halcyon]

This reasoning assumes that the alternator is able to put out 14,4 V into a large, heavily depleted service bank. Is that realistic?
I think in most cases the voltage initially would be at 13,5 or lower and only reach 14,4 when the bank's SOC gets close to 75 - 80 percent.
At that point the current will be much lower and the voltage drop over the service bank diode will be more or less similar to that of the starter battery's.

In the above case this would mean you are assuming a small alternator in proportion to bank size, around 10 - 20% to give slow charge. A high charge rate would give a high charge voltage quickly through surface charge of the service bank. It then depends on diode size, small diode splitter matching alternator size will have the bigger volt drop than a large diode carrying a smaller current.

Assuming a slow charge, low initial charge voltage, through a small diode will give a reasonably constant high charge current to regulation voltage, current tailing slightly after 14 volt. The engine battery being smaller will reach the higher alternator voltage faster and current will tail off, volt drop falling as current drops. You also need to factor in charge lost heating the atmosphere.

Blocking diodes go back to the late 60's, and always were a problem with volt drop, we bought out the VSR in 78 avoid the volt drop, but also to maintain permanent connection of the alternator to the engine battery, so even total splitter failure would not effect engine battery charge, plus no engine charge system mods needed.

Brian

 

[sailinglegend420]

This reasoning assumes that the alternator is able to put out 14,4 V into a large, heavily depleted service bank. Is that realistic?
I think in most cases the voltage initially would be at 13,5 or lower and only reach 14,4 when the bank's SOC gets close to 75 - 80 percent.
At that point the current will be much lower and the voltage drop over the service bank diode will be more or less similar to that of the starter battery's.

That is a fair comment for those boats that don't have a properly sized "hot rated" marine alternator - and I am afraid too many boats are like this. I should have said my example was a worse case scenario. With a shorepower charger feeding these split diodes the charger will easily reach 15.8 volts.

If you take my example and re-do the maths so that the volt drop across the service battery is 1.0v instead of 1.4, and the alternator can get up to 15.4 volts, then the starter battery will still be seeing 14.7 volts. A sealed battery that should be at 14.1v - 14.4v will still not be happy.

As I said, in all cases with Split Diodes the voltage sensing must never be on one of the batteries.

Only a few weeks ago when doing some battery tests I disconnected all cables and I forgot to replace the DC generator voltage sense wire. When I next ran the generator the voltage alarm immediately went off and the generator was up to 17 volts!!!!

 

[BabaYaga]

That is a fair comment for those boats that don't have a properly sized "hot rated" marine alternator - and I am afraid too many boats are like this. I should have said my example was a worse case scenario. With a shorepower charger feeding these split diodes the charger will easily reach 15.8 volts.

If you take my example and re-do the maths so that the volt drop across the service battery is 1.0v instead of 1.4, and the alternator can get up to 15.4 volts, then the starter battery will still be seeing 14.7 volts. A sealed battery that should be at 14.1v - 14.4v will still not be happy.

As I said, in all cases with Split Diodes the voltage sensing must never be on one of the batteries.

Only a few weeks ago when doing some battery tests I disconnected all cables and I forgot to replace the DC generator voltage sense wire. When I next ran the generator the voltage alarm immediately went off and the generator was up to 17 volts!!!!

I quite agree that a powerful hot rated alternator and diodes are unlikely to be a good combination. Those figures look more realistic. IMO time on over voltage is an important factor and in that respect a shorepower charger connected trough diodes is perhaps even worse?
Every method for charge splitting has merits and drawbacks, depending on the configuration. Beside VSR's and diodes there is also the simple relay activated by alternator D+ – often overlooked but worth considering.

 

[john_morris_uk]

That's the best reason yet that I've heard for going VSRs. One of our split diodes went open circuit and the starter battery went flat. Luckily the voltage sense was on the alternator.

With split diodes the voltage sensing must never be on one of the batteries for another very good reason. Sorry to disagree, but this is tosh. You just need some over voltage protection on your charging system.

Consider a heavily depleted large service bank - and an almost full smaller starter battery. The voltage drop across the diode feeding the service bank increases with the current so may well reach 1.4 volts or more. If the alternator senses the voltage at the service bank it will raise the alternator output by 1.4 volts to say 15.8 volts to get 14.4v at the battery. I humbly challenge your knowledge of the PN junction and the internal resistance of diodes. The voltage drop across the diode feeding the starter bank is only 0.7 volts because the smaller service bank is taking a much much smaller current. So the starter battery is sitting at 15.1 volts for maybe several hours! This is almost an equalizing charge - so not very good for any sealed, Gel, and AGM batteries.

In the above case this would mean you are assuming a small alternator in proportion to bank size, around 10 - 20% to give slow charge. A high charge rate would give a high charge voltage quickly through surface charge of the service bank. It then depends on diode size, small diode splitter matching alternator size will have the bigger volt drop than a large diode carrying a smaller current. See my comments about the PN junction and voltage drop. Its conceivable that a VERY underrated diode might have some additional resistance, but one would be very foolish to fit such a diode to a charging system.

Assuming a slow charge, low initial charge voltage, through a small diode will give a reasonably constant high charge current to regulation voltage, current tailing slightly after 14 volt. The engine battery being smaller will reach the higher alternator voltage faster and current will tail off, volt drop falling as current drops. You also need to factor in charge lost heating the atmosphere.

Blocking diodes go back to the late 60's, and always were a problem with volt drop, we bought out the VSR in 78 avoid the volt drop, but also to maintain permanent connection of the alternator to the engine battery, so even total splitter failure would not effect engine battery charge, plus no engine charge system mods needed.

Brian

With respect you are not exactly disinterested. I don't want to appear to be banging the drum for diode splitters, but lets get the facts straight...

That is a fair comment for those boats that don't have a properly sized "hot rated" marine alternator - and I am afraid too many boats are like this. I should have said my example was a worse case scenario. With a shorepower charger feeding these split diodes the charger will easily reach 15.8 volts.

If you take my example and re-do the maths so that the volt drop across the service battery is 1.0v instead of 1.4, and the alternator can get up to 15.4 volts, then the starter battery will still be seeing 14.7 volts. A sealed battery that should be at 14.1v - 14.4v will still not be happy.

As I said, in all cases with Split Diodes the voltage sensing must never be on one of the batteries. Where else would you put it? If you sense from alternator side, you will get all the problems that diodes get a bad press for. The easy and obvious answer is to ensure that your alternator charging regulator has some over voltage protection. We happen to have a Sterling system, and it has just such protection. Anyone wanting to ensure they have an efficient battery management system will install some sort of smart alternator regulator. With such a device, over voltage protection is common and counters many of the arguments.

Only a few weeks ago when doing some battery tests I disconnected all cables and I forgot to replace the DC generator voltage sense wire. When I next ran the generator the voltage alarm immediately went off and the generator was up to 17 volts!!!!

I will say again: I don't wish to argue that VSR's are rubbish, or that diodes don't have their problems, but none are insurmountable.

I don't understand the comments about mains chargers through diodes. Such a way of wiring a charger would be fraught with problems. However many marine smart chargers have a choice of outputs. We have mains charger (which also happens to be a Sterling one) and it has the option for three separate and I dependant outputs. Two are tied together and feed the domestic bank and the remaining one goes to the engine start battery. None of them go through the diode splitter, as the charger sorts it all out by itself.

Out of interest, the engine start battery is the same one we have been using for the last ten years (and there is no sign yet that it has been suffering any from 'over voltage' from when the domestic bank is charging.) The previous domestic bank of batteries lasted 6 years and I feel they only got trashed by the boat being left on its mooring all winter and me mucking up a timer for some systems we were running and running the domestic bank flat and destroying it.

Our set up is: engine alternator, diode splitter, battery sensed from the domestic bank to a Sterling Alternator charge controller, 425 Ah of wet deep discharge batteries. Mains charger as already described. Wind generator via a regulator to the domestics. The whole system is monitored: Volts (and Amps in and out of each battery banks), plus a measure of Ah used and returned by the charging system. It happens to be our system and it works very well, but VSR's can also work very well.

 

[sailinglegend420]

I don't want to appear to be banging the drum for diode splitters, but lets get the facts straight...

"I humbly challenge your knowledge of the PN junction and the internal resistance of diodes."

Your double posting doesn't make you doubly right! - by the way you can go in and edit and delete a post.

Please check out the first google search I found from Wikipidea which confirms my posting, and I quote:

"At higher currents the forward voltage drop of the diode increases. A drop of 1 V to 1.5 V is typical at full rated current for power diodes."

I don't understand the comments about mains chargers through diodes. Such a way of wiring a charger would be fraught with problems.

My large DC generator has one DC output. My expensive Victron shorepower charger has a small second output for the starter. If I wanted a large output to power a second bank - bowthruster - then a split charging solution would be needed. Split Diodes would not do the job.

As I said, in all cases with Split Diodes the voltage sensing must never be on one of the batteries.Where else would you put it? If you sense from alternator side, you will get all the problems that diodes get a bad press for.

I'm afraid that's where they have to go - and then accept the bad press.

You have to accept that "what works OK for you" may not work on other boats with different installations! It may work, but it may not "Best Practice"!

 

[john_morris_uk]

Your double posting doesn't make you doubly right! - by the way you can go in and edit and delete a post.

Please check out the first google search I found from Wikipidea which confirms my posting, and I quote:

"At higher currents the forward voltage drop of the diode increases. A drop of 1 V to 1.5 V is typical at full rated current for power diodes."



My large DC generator has one DC output. My expensive Victron shorepower charger has a small second output for the starter. If I wanted a large output to power a second bank - bowthruster - then a split charging solution would be needed. Split Diodes would not do the job.


I'm afraid that's where they have to go - and then accept the bad press.

You have to accept that "what works OK for you" may not work on other boats with different installations! It may work, but it may not "Best Practice"!

Thank you and I know about deleting posts but it seems to have sorted itself out. edit: Its come back again so I've deleted it!

In response I might reply that just restating your incorrect assertions doesn't make your argument any the better either.

Wikipedia is notoriously unreliable and knowing its inaccuracy in some of the more obscure areas of electronics, I rarely if ever refer to it and certainly wouldn't accept it as a valid source for 'proving an argument'. I hope that you would agree that if you had a diode that was so underrated that you were getting that sort of voltage drop it would be the wrong diode for the system and you would be asking for trouble and looking at significantly reduced MTBF. Have you ever measured voltage drops on PN junctions? All this is slightly irrelevant as monitoring the battery voltage (and ideally temperature) at the battery is the ONLY proper way of ensuring efficient charging regimes. In larger installations this applies to mains chargers as well.

I have no doubt that there are specific circumstances in which triple battery banks and chargers with only two outputs would lead you to NOT using a splitter diode, but citing a specific and special situation to prove the general case is not helpful. Therefore I respectfully suggest that it certainly doesn't 'prove your case'.

However, I would still freely admit that VSR's can be a perfectly satisfactory solution, but I don't see any authority citing them as 'best practice'. On what basis do you make this claim?

Splitter diodes appear to be simple and easy to fit devices and gained a bad reputation from being fitted incorrectly. Fitted correctly with battery sensing and protection against over voltage they are fit and fogey* devices that never wear out and rarely fail.

Nearly all boats have one (or more usually two) battery banks. A diode splitter fitted correctly is a perfectly valid solution and in this context, VSR's have no advantage and some disadvantages.

* I mean 'forget' (dratted spelling checker!) but it was such a wonderful Malapropism I've left it. (As others have suggested diode splitters as 'past it' and therefore old hat, fogey seems particularly and wonderfully inappropriate word to have ended up in my sentence.)

 

[sailinglegend420]

..In response I might reply that just restating your incorrect assertions doesn't make your argument any the better either.

Wikipedia is notoriously unreliable and knowing its inaccuracy in some of the more obscure areas of electronics.....

I expected an attack on Wikipedia so I have done a lot more searches and it is easy to find dozens of references to the voltage drop across POWER DIODES rising as current rises. Eminent professors, books on automotive power designs, numerous graphs and references to voltage between 1.1v and 1.6v drop with high currents. Anybody who is seriously interested can do their own searches. Even Mr Sterling admits there is a higher voltage drop as the current increase - which is why he recommends ultra low loss splitters. These are the only split diodes that should be used, but they are much more expensive.

I should credit the originator of these ideas of high current - high voltage drop - with battery sensing - causing high voltage on the starter battery.

See this very good but lengthy appraisal from the Moody Owners Association:

http://leisureowners.memberlodge.org/Resources/Documents/battery_management.pdf

The only point he missed is pvb's posting:

...Diodes usually fail open circuit. If the diode leg supplying the battery with the battery-sensing lead attached fails open circuit, the alternator voltage will soar and it will cook the other battery. In many cases, the first you'll know is the awful acrid smell of boiling acid....

On the question of "Best Practice" for Split Charging I fear no "Best Practice" yet exist.

Ultra Low Loss splitters are a "Better" practice.

VSR's are "Betterer" EDIT: than normal Split Diodes.

DC-DC battery chargers like the Balmar DuoCharge are even better because can be adjusted to different Absorption and Float voltages, but it is still a voltage follower like the EchoCharge. It only goes to Float if the source battery goes to float.

"Best Practice" would be a Balmar DuoCharge with automatic multi-stage charging. Balmar saying they are looking this, but fear it will be too expensive because the market would be too small.

 

[john_morris_uk]

I expected an attack on Wikipedia so I have done a lot more searches and it is easy to find dozens of references to the voltage drop across POWER DIODES rising as current rises. Eminent professors, books on automotive power designs, numerous graphs and references to voltage between 1.1v and 1.6v drop with high currents. Anybody who is seriously interested can do their own searches. Even Mr Sterling admits there is a higher voltage drop as the current increase - which is why he recommends ultra low loss splitters. These are the only split diodes that should be used, but they are much more expensive.

I should credit the originator of these ideas of high current - high voltage drop - with battery sensing - causing high voltage on the starter battery.

See this very good but lengthy appraisal from the Moody Owners Association:

http://leisureowners.memberlodge.org/Resources/Documents/battery_management.pdf

The only point he missed is pvb's posting:


On the question of "Best Practice" for Split Charging I fear no "Best Practice" yet exist.

Ultra Low Loss splitters are a "Better" practice.

VSR's are "Betterer"

DC-DC battery chargers like the Balmar DuoCharge are even better because can be adjusted to different Absorption and Float voltages, but it is still a voltage follower like the EchoCharge. It only goes to Float if the source battery goes to float.

"Best Practice" would be a Balmar DuoCharge with automatic multi-stage charging. Balmar saying they are looking this, but fear it will be too expensive because the market would be too small.

The only point I would take issue with is your VSR's are 'betterer'. It's only your opinion but one you are perfectly entitled to. I try not to be so dogmatic about things that are open to debate. My hackles do rise when people (this is not necessarily aimed at you) start spouting things as gospel when they are not.

 

[pvb]

The only point I would take issue with is your VSR's are 'betterer'. It's only your opinion but one you are perfectly entitled to. I try not to be so dogmatic about things that are open to debate. My hackles do rise when people (this is not necessarily aimed at you) start spouting things as gospel when they are not.

But VSRs are better (if not "betterer") simply because their mode of possible failure doesn't have major potential consequences.

 

[sailinglegend420]

The only point I would take issue with is your VSR's are 'betterer'....

AS you posted I was editing this:

VSR's are "Betterer" EDIT: than normal Split Diodes.